In a prospective longitudinal study 89 men with HIV-1 infection were observed for a mean time of 51 months with regard to clinical signs and laboratory findings predictive of progression to AIDS/opportunistic infection (OI). In a bivariate regression analysis the clinical signs showing a significant relation to AIDS development were: dermatitis of the face, yellow toe nail changes, hairly leukoplakia and oral candidiasis. The laboratory findings significantly associated with progression to AIDS were: decrease of the relative and absolute number of CD4 lymphocytes, decrease of the CD4/CD8 ratio, HIV p24 antigenaemia, lack of anti-HIV p24, elevated erythrocyte sedimentation rate, anaemia and elevated serum-beta-2-microglobulin. The relative number (%) of CD4 cells was found superior to the absolute number and the CD4/CD8 ratio. In a multivariate regression analysis decrease of CD4 lymphocytes and lack of anti-HIV p24 were independently associated with subsequent AIDS/OI development.